A projection keyboard is a virtual keyboard that can be projected onto a surface and components of the keyboard detect finger movements and translate the movements into keystrokes on a device. A projection keyboard unit generally includes a laser to project a visible virtual keyboard onto a surface (e.g., a red diode laser as a light source to project a full size QWERTY layout keyboard, with a size of 295 mm×95 mm projected at a distance of 60 mm from the projection keyboard unit), and a sensor or camera to sense finger movements. A location or detected co-ordinates of the finger can be used to determine actions or characters to be generated.
A projection keyboard may also use a second (invisible infrared) beam projected above the virtual keyboard. In this example, as a finger makes a keystroke on the virtual keyboard, the finger breaks the infrared beam and infrared light is reflected back to a camera. Reflected infrared beam may pass through an infrared filter to the camera, and the camera can photograph an angle of incoming infrared light. A sensor may determine where the infrared beam was broken, and detected coordinates can be used to determine actions or characters to be generated.
A projection keyboard may include use of a micro-controller to receive positional information corresponding to reflected light or light flashes from the sensor, and to interpret events to be communicated through an appropriate interface to external devices. Events may include a key stroke, mouse movement or touchpad control.